Thermally Activated Delayed Fluorescence in Neutral and Cationic Copper(I) Complexes with the 2-(4-Thiazolyl)benzimidazole Ligand

Thiswork studies the influence of the diphosphane and thecharge in the emissive properties of complexes [Cu(P<<^>>P)(Htbz)]PF6, Htbz = 2-(4-thiazolyl)benzimidazole] and the correspondingneutral analogous [Cu(P<<^>>P)(tbz)], obtained by deprotonation of thediimine ligand. TADF has been found for the blue or green emitters[Cu(P<<^>>P)(Htbz)]PF6 and [Cu(dpephos)(tbz)] with & UDelta;E(S-1-T-1) values between 658and 455 cm(-1). Theoretical calculations reveal adifferent origin for the absorptions, leading to the observed emissions. Cationic [Cu(P<<^>>P)(Htbz)]PF6 [P<<^>>P = xantphos,dpephos;Htbz = 2-(4-thiazolyl)benzimidazole] and the corresponding neutralcomplexes [Cu(P<<^>>P)(tbz)], obtained through deprotonation of the diimineligand, have been synthesized with the aim of analyzing the role ofthe diphosphane and Htbz deprotonation in the emissive propertiesof these complexes. For the study of the diphosphane effect, the luminescenceproperties of these compounds have been compared with those of thereported analogous derivatives with Htbz and carborane diphosphanes.Complexes [Cu(P<<^>>P)(Htbz)]PF6 (P<<^>>P = xantphos, dpephos)and [Cu(dpephos)(tbz)] display thermally activated delayed fluorescence,which has been studied, revealing a & UDelta;E(S-1-T-1) between 658 and 455 cm(-1). Theoretical calculations indicate different origins for the absorptions,leading to the observed emissions.